I saw the fix in the beta, not sure if that were an attempt at fixing one of the two mutually exclusive fix you mentioned but I wrote this script:
alias testbase {
var %r1 $r(1,1000000000),%r2 $r(1,1000000000)
var %calc $calc(%r1 / %r2)
if ($base(%calc,10,10) != %calc) echo -sg %r1 %r2 $v1 $v2
}
ran on a timer -m 1 10, which unfortunately quickly echoed 267169000 622827430 0.42962 0.428962
But it seems then that it is a misconception from scripters to expect the same result with decimals in $base with same inbase/outbase.
My suggestion about using the number as is with same inbase/outbase would bypass the rounding issue.